The present invention relates to methods for controlling the migration of unconsolidated particulates in a portion of a subterranean formation, and more particularly, to the using a pressure pulse to enhance the effectiveness of placement of a consolidation fluid in a portion of a subterranean formation.
Hydrocarbon wells are often located in unconsolidated portions of a subterranean formation, that is, portions of a subterranean formation that contain particulate matter capable of migrating with produced fluids out of the formation and into a well bore. The presence of particulate matter, such as sand, in produced fluids may be disadvantageous and undesirable in that such particulates may abrade pumping equipment and other producing equipment and may reduce the fluid production capabilities of the producing portions of the subterranean formation. Unconsolidated portions of subterranean formations include those which contain loose particulates that are readily entrained by produced fluids and those wherein the particulates are bonded together with insufficient bond strength to withstand the forces produced by the production of fluids through the zones.
One conventional method used to control formation particulates in unconsolidated formations involves consolidating a portion of a subterranean formation into a hard, permeable mass by applying a curable resin composition to the portion of the subterranean formation. In one example of such a technique, an operator pre-flushes the formation, applies a resin composition, and then applies an after-flush fluid to remove excess resin from the pore spaces of the zones. Such resin consolidation methods are widely used but may be limited by the ability to place the resin through enough of the unconsolidated portion of the formation to adequately control the particulates. Even when the resin compositions are designed with very low viscosities, they are often unable to achieve significant penetration or uniform penetration into the portion of the subterranean formation. Conditions such as variable formation permeability; formation damage in the near-well bore area; debris along the well bore, a perforation tunnel, or a fracture face; and, compaction zones along the well bore, a perforation tunnel, or a fracture face may make uniform placement of resin compositions extremely difficult to achieve. The problems are particularly severe when used to treat long intervals of unconsolidated regions.
In production operations, hydrocarbons may be profitably extracted from the reservoir by a variety of recovery techniques. One such technique is pressure pulse waterflooding. Generally, the combination of a secondary recovery technique, e.g., waterflooding, with the use of pressure pulsing is thought to enable the recovery of up to about 30% to about 45% of the reserves. Pressure pulsing as referred to herein will be understood to mean deliberately varying the fluid pressure in the subterranean reservoir through the application of periodic increases, or “pulses,” in the pressure of a fluid being injected into the reservoir. Pressure pulsing has also been performed through the use of a pulse-generating apparatus attached to a well head located above the surface. Pulsing typically occurs either by raising and lowering a string of tubing located within the well bore, or by employing a flutter valve assembly which periodically opens and closes to permit a fluid to be pumped into the well bore.
While such pressure pulsing techniques have been used to enhance water injection for secondary oil recovery, they have not been used to insert resins or formation consolidation type fluids into a formation. The present invention seeks to use the increase flow benefits of pressure pulsing to increase the ability of a resin composition to penetrate a portion of a subterranean formation.